1. Field of the Invention
The present invention generally relates to active infrared (IR) location systems for enhanced reflectance targets. Such systems normally employ a pulsed illuminator combined with a directional optical reflection detector on a search vehicle, and a retro-reflector located on the object to be found.
2. Description of Prior Art
Electronic imaging of optical and infrared returns from retro-reflectors such as corner cubes, "Scotchlite" or other similar devices is severely limited in daylight by solar background illumination. The use of a laser and a wavelength matched narrow bandpass filter on the receiver can significantly improve performance, but the sensor will still suffer from reduced performance during the day. Even with this technique, daylight background radiation still remains a limiting factor which previously could be overcome by using high average power lasers. This leads to complexities in the laser design such as the need for cooling equipment and large power supplies, both of which add cost and weight. Further, the use of additional power compounds the eye-safety difficulties. What is needed in this instance is a reliable location system of the type described above which requires an illuminator that emits a very low average power.
It is therefore one object of the invention to provide a method of locating friendly reflectors which provides a high signal to background ratio during both dark night and bright day. It is another object of the present invention to provide a system to carry out such a method.